Operation Distant Plain
Operation Distant Plain was a series of non-nuclear explosive and detonable gas tests performed on test sites in Alberta, Canada during the course of 1966 and 1967. Their purpose was to provide airblast, cratering and ground shock data in summer and winter conditions for testing new prototype equipment, military targets and coniferous forest blowdown and defoliation. Participants included Canada, United Kingdom, Australia and United States under the Tripartite Technical Cooperation Program. Detonable gas balloons were used in this operation in an attempt to find an economical substitute for TNT as well as for the fact that they could be placed at desired heights without a heavy support structure or towers. In addition, they were more adaptable to airblast phenomena and produced a well defined blast wave without perturbation or ejecta; they also produced no crater. However, it was found that they lacked the high pressure associated with high explosives, and difficulties were encountered as the 20-ton gas balloon ruptured and another detonated unexpectedly during inflation. Ultimately ANFO was elected as a lower cost alternative to TNT for non-nuclear explosives tests.
Tests
The following table summarizes the events that took place during the operation in chronological order.| Event | Date | Charge | Yield | Height of Burst | Location | Notes |
| 1 | 7 July 1966 | TNT sphere, tower | 20 | 85 | Drowning Ford Test Range, SES | Airblast and induced ground motions |
| 2 | July 1966 | 125 foot methane-oxygen balloon | 20 | 85 | Drowning Ford Test Range, SES | Cancelled, balloon ruptured during inflation |
| 2A | 22 July 1966 | 125 foot propane-oxygen hemisphere | 20 | 0 | Drowning Ford Test Range, SES | Test feasibility of detonable gas, compare with 20 ton TNT events |
| 3 | 27 July 1966 | TNT sphere, half buried | 20 | 0 | Drowning Ford Test Range, SES | Normal environment control for Event 5 |
| 4 | 16 August 1966 | TNT Hemisphere | 50 | 0 | Edson Forest, 10 miles northwest of Hinton | Coniferous forest blowdown test |
| 2B | October 1966 | 125 foot methane-oxygen balloon | 18.6 | 63 | Drowning Ford Test Range, SES | Rescheduled Event 2, detonated unexpectedly during inflation on ground |
| 5 | 9 February, 1967 | TNT sphere, half buried | 20 | 0 | Drowning Ford Test Range, SES | Frozen ground test |
| 6 | 26 July 1967 | TNT sphere, supported | 100 | 0 | Watchdog Hill Blast Range, SES | Nuclear weapon surface burst simulation |
| 1A | 18 August 1967 | TNT sphere, tower | 20 | 30 | Watchdog Hill Blast Range, SES | Airblast and induced ground motions, repeat of event 1 |